Why is phenol red added to the test tubes during ion and gas tests?

• A. To act as a pH indicator and show changes in acidity or alkalinity.
• B. To increase the rate of gas production in reactions.
• C. To precipitate metal ions for easier identification.
• D. To neutralize any acids formed during the test.

Answer: (A)

Verified step by step guidance

1. Understand that phenol red is a chemical compound commonly used as a pH indicator in various chemical tests.
2. Recall that a pH indicator changes color depending on the acidity or alkalinity of the solution it is in, which helps visually identify pH changes during reactions.
3. In ion and gas tests, phenol red is added to detect the formation of acidic or basic gases or ions by showing a color change, indicating a shift in pH.
4. Recognize that phenol red does not increase reaction rates, precipitate ions, or neutralize acids; its primary role is to signal pH changes through color variation.
5. Therefore, phenol red helps chemists observe and interpret the results of ion and gas tests by acting as a visual pH indicator.